The position in the canopy and the bearing status of 1-year-old shoots affect the bearing potential and morphology of current-year shoots in walnuts (Juglans regia L.) cv. Chandler
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From 1 year to the next the number of shoots increases, but their individual size declines. Shoots located in more lightened canopy zones and bearing two fruits maintain productive sustainability.
432 shoots in 24 mature trees from three commercial orchards located in the central valley of Chile were inspected for 2 years. Tree canopy was divided into three zones according to light exposure (upper, lower-exposed, lower-shaded). In the first year of the study, six shoots were randomly selected in each canopy zone and divided into three bearing statuses [shoots bearing one fruit (F1), shoots bearing two fruits (F2), and shoots bearing three fruits (F3)]. In the second year, all new shoots (1068) born on the 432 shoots were studied. Specific leaf weight and current-year shoots (CY) characteristics (length, diameter, number of leaves, number of leaflets, leaf area) were evaluated as a function of the previous season fruit load and canopy position of the 1-year-old (1Y) shoots. The results indicated that 1Y shoots located in more light-exposed canopy zones bore on average 0.5 more CY shoots than 1Y shoots in the lower-shaded canopy zone. Specifically, the 1Y shoot probability of bearing CY shoots that had two or three fruits was 72.8% in the upper canopy zone, 44.6% in the lower-exposed zone, and 34.9% in the lower-shaded zone of the canopy, respectively. 1Y shoots in the lower-shaded zone had on average a 7.7% higher probability of dying than 1Y shoots in the upper and exposed positions. In addition, CY shoots born on 1Y shoots exposed to light were on average 2.7 cm longer, more than 1 mm thicker, and had 53.7% greater leaf area than CY shoots born on shaded 1Y shoots. Finally, the results of this study showed that 1Y shoots that had two fruits in the previous season produced CY shoots with the greatest bearing potential in the current and future seasons.
KeywordsBearing structure Light Leaf area Source Sink
The authors would like to thank Chilenut AG for the Specific Agreement which financed the project called “Estudio del crecimiento y morfología de las ramillas del nogal en plena producción para la evaluación de los principales componentes de rendimiento”.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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